Spatial light modulators are arrays of one or more devices that can control or modulate an incident beam of light in a spatial pattern that corresponds to an electrical input to the devices. The incident light beam can be modulated in intensity, phase, polarization or direction. Some modulation can be accomplished through the use of Micro-Electromechanical System devices or MEMs that use electrical signals to move micromechanical structures to modulate light incident thereon. Spatial light modulators are increasingly being developed for use in various applications, including display systems, optical information processing and data storage, printing, and maskless lithography.
A class of spatial light modulators include a single MEMS device or a linear array of MEMS devices configured to paint two-dimensional patterns. For many applications, such as printed-circuit board (PCB) patterning/printing, display systems, printing and/or relatively moderate range semiconductor processing, spatial light modulators such a one-dimensional MEMS device provides a suitable solution.
However, for many other applications requiring high or very high resolution, such as leading edge semiconductor processing, spatial light modulators having a two-dimensional array of MEMS devices would be preferred.
The appeal of 2D MEMS spatial light modulators has been evidenced in the widespread adoption of the Digital Mirror Device (DMD) from Texas Instruments. With its large étendue, this device can be used with incoherent lamp sources and conventional optics to create high-quality images. Despite its success in display applications, however, the DMD has not been embraced for many applications, for example mask-less lithography. This is primarily due to shortcomings in (a) analog gray-scale capability, (b) modulation speed, and (c) diffraction efficiency.
Accordingly, there is a need for a two dimensional spatial light modulator that exhibits the following characteristics: a large étendue, good analog gray-scale capability, high modulation speed, and high diffraction efficiency. There is a further need for a method of manufacturing such a spatial light modulator that is simple, cost-effective, and tolerant of process variations.